The present invention relates to a method of forming gasket with an annular sealing projection and a sealing groove formed around a hole to be sealed.
In a conventional gasket, in order to seal around a hole, such as a cylinder bore, water hole, oil hole and so on, various sealing devices have been used. A bead is often formed around the hole to provide a surface pressure thereat. However, if only a bead is formed around the hole, a fluid in the hole may pass over the bead due to change of the surface pressure at the bead.
Therefore, in addition to or separately from the bead, a plate for the gasket may be turned around a hole to be sealed to provide a surface pressure around the hole. However, since a part of the metal plate is turned, the thickness of the gasket is increased at the turned portion. This is not preferable when a thin gasket is required. Especially, in case a gasket is formed of one metal plate, the turned portion is not preferable.
Also, a shim may be formed on a metal plate around a hole to be sealed, such as disclosed in U.S. Pat. No. 4,776,073. In this case, the shim with a proper thickness is selected, and attached onto the metal plate by welding and so on. Therefore, it takes time and labor when the shim is used. Also, it is difficult to attach a thin shim on the metal plate.
In Japanese Patent Publication (KOKAI) No. 7-91548, a gasket has a thick portion and a groove around a hole to be sealed.
However, the thick portion is not ideally arranged to properly seal around the hole. Also, when the thick portion is formed, the metal plate is excessively processed, so that the plate to be used is limited.
In view of the above, the present invention has been made, and an object of the invention is to provide a method of forming a thin metal gasket, which can provide a non-resilient surface pressure around a hole to be sealed.
Another object of the invention is to provide a method of forming a thin metal gasket as stated above, wherein the surface pressure around the hole can be selected as desired.
A further object of the invention is to provide a method of forming a thin metal gasket as stated above, which can be manufactured easily without substantial limitation for the metal plate.
Further objects and advantages of the invention will be apparent from the following description of the invention.